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OCT Offers High Speed, Strong Resolution in Retinal Imaging

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JOEL WILLIAMS, ASSOCIATE EDITOR
[email protected]

Researchers at the University of Washington have modified the standard process of OCT (optical coherence tomography) to detect minute changes in response to light in individual photoreceptors in the living eye. The technique has potential in the testing of therapies such as stem cells or gene therapy to treat retinal disease.

“Typically, retinal OCT systems are implemented by raster scanning a point of light across the retina. This provides excellent contrast, but at the cost of speed due to dual-axis scanning,” corresponding author Ramkumar Sabesan, assistant research professor of ophthalmology, told Photonics Media. “On the other end, full-field OCT systems exist that can operate at higher speeds, but have lower resolution and contrast. A line-scan OCT sits in the middle, and allows an excellent opportunity to optimize speed, sensitivity, and resolution for high-resolution retinal imaging.”

The researchers built a high-speed line-scan spectral OCT with adaptive optics. In a line-scan OCT, a linear broad spectral band illumination is shined on the retina, and the backscattered light is captured after diffraction on a 2D sensor. By virtue of parallel acquisition of an entire retinal cross-section (B-scan) in a single high-speed camera frame, Sabesan said, depth-resolved tomograms at speeds up to 16 kHz were achievable in this study. Implementing phase-resolved OCT acquisition allows monitoring of nanometer-scale optical changes in response to light.

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“The high speed allows tracking fast retinal events corresponding to light-evoked electrical activity in photoreceptors, by overcoming the ever-present eye motion in a living human,” Sabesan said. “Adaptive optics allows correcting the eye’s native aberrations and visualizing these minute nanometer-millisecond-scale physiological events in individual cells.”

Because photoreceptors are the primary cells affected in retinal generation and the target of many treatments, noninvasive high-resolution visualization of their physiology is invaluable, the researchers said in their paper.

“We hope the technology will serve as an early, safe, and highly sensitive retinal biomarker and serve two purposes in the clinic,” Sabesan told Photonics Media. “First it will help understand the mechanisms and time-course of dysfunction in disease and response to existing therapies. Second, it will help evaluate the safety and efficacy of new therapies on the horizon.”

The research was published in Science Advances (www.doi.org/10.1126/sciadv.abc1124).

Published: September 2020
Glossary
optical coherence tomography
Optical coherence tomography (OCT) is a non-invasive imaging technique used in medical and scientific fields to capture high-resolution, cross-sectional images of biological tissues. It provides detailed, real-time, and three-dimensional visualization of tissue structures at the micrometer scale. OCT is particularly valuable in ophthalmology, cardiology, dermatology, and various other medical specialties. Here are the key features and components of optical coherence tomography: Principle of...
eye
The organ of vision or light sensitivity.
line scan
Line scan refers to a method of capturing images or data by scanning a single line at a time, as opposed to capturing the entire image simultaneously. This technique is commonly used in various imaging and scanning applications where a continuous or sequential scan along a line is more practical or efficient than capturing the entire image at once. Key features of line scan imaging include: Sequential capture: Instead of capturing an entire two-dimensional image at once, line scan systems...
adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of atmospheric distortions. The Earth's atmosphere can cause light passing through it to experience distortions, resulting in image blurring and degradation in various optical applications, such as astronomical observations, laser communications, and imaging systems. Adaptive optics systems actively adjust the optical elements in real-time to compensate for these distortions. Key...
Research & Technologyoptical coherence tomographyOCTeyeretinal imagingline scanImagingdiagnosticcamerasLasersOpticsadaptive opticsUniversity of WashingtonBioScan

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